Temperature control for a compartmental vehicle



June 30, 1964 B. R. LEIGH ETAL TEMPERATURE CONTROL FOR A COMPARTMENTALVEHICLE Filed Dec. 19, 1961 @www LOW L lH PTH

Unitedg StatesvPatent O TEMPERATURE CGNTRL FR A COMPARTMENTAL VEHICLEBertram Robert Leigh, Rickmansworth, Leonard George Thomas, LondomandRoger Lund Lack, Bromley,

Kent, England, assignors to J. Stone & Company (Deptford) Limited,London, .England Filed Dec'. 19, 1961, Ser. No. 160,623

Claims priority, application Great Britain Dec. 20, 1960 This inventionconcerns improvements relating to temperature control for acompartmental vehicle, especially a railway coach, in whichzheating in'individual compartments is under the control of the occupants. Anarrangement for such temperature-control is described and' claimed inthe` specification of our patent application Serial No. 728,710, nowPatent No. 3,028,471, and the ypresent invention is, at least in somerespects, concerned with improvements upon ormodiiications of thetemperature-control arrangement claimed in that patent.

According to the said patent, an arrangement for controlling the,temperature in compartments of a vehicle supplied with air from acommon air-conditioning or heating equipment comprises in combinationwith ya mainr thermostat controlling .the said equipment and arranged tobeV influenced bythe temperature of the air at a com-l mon return-airpoi ut, individual electric heaters for respective compartments,separately controllable switches for the said heaters7 and meansdependent upon'the current supplied tothe compartment heaters forautomaticallyl n vto about 721/2 and 75 F. respectively. The heaters 5are f Vpartment.

peratur'e in the compartment might be 70, determined Patented une 30,1964 Jce lated D.C. direct current, at 35 volts say, by Way. of theswitch Zand earth. v

In addition to the main heating, however, each compartment 4 of thecoach is provided with small electrical heatersy 5 under the control, byswitches 6, of the occupants. T he heaters 5 for each compartment may inprac-` tice be controlled by a switch having ythree positions, an oilposition, a position switchingon one heater 5 and a position switchingon both heaters 5, thus giving three different conditions of so-calledrehea in that com- For example, with the ofi position, the temby thecontrol of the main heatersheating the air supplied t0 the compartment.With the second and third position of the switch, the temperature mightbe raised connected to a source of supply of alternating current vthrough a main switch 7.

As explained in the aforesaid specication, it is neces-V sary, if thisarrangement is to be eIiectiveQthat the main thermostats 1 should havetheir temperature settings raised progressively as more reheatisswitched on by the occupants of the compartments. 4. Following theabove example, in the extreme case, if all the heaters Shave beenswitched on to give 75 F. in all the compartments, then the settings ofthe thermostats 1 would have also to be raised to 75. if this were notdone and the settings were left at, say, 70 F., the only result would bethat raising the effective setting` of the main thermostat whenindividual compartment heating is switched on. kWith a mainthermostat'of the known heater-bias type, the bias 'applied could becaused to be varied in dependence upon the total current supplied forindividual compartthemain heaters would have less work to do, thetemperatures in the compartments remaining at 70 F. Furthermore, if theheaters 5 iu one compartment were then switched oli, the temperature inthat compartmentwould fall to nearly 65 F.

yForyeffecting progressive adjustment of the setting of the mainthermostats in the above-described arrangement,

the sunt total of .thev currents suppliedvto the heaters 5` n yis passedthrough the primary 8 ofa' current transformer has a negativecoefficient of resistance and which is itselfvr heated to an extentdependent upon the said total current.

, ln other Words, the resistor is used as a transform element whichkeffects a change in the rsetting of the main thermostat or thermostatsin dependence upon the amount of individual compartment heating switchedon.

One manner of carrying the invention into etlect will now be more fullydescribed by way of example and with reference to the'accompanyingdrawing, ywhich is a circuit diagram ofrelevant yparts of a controlLarrangeing for which is suppliedV by heaters (not shown) which heatcirculated airsupplied to thecompartments from ay i ycommon air-heatinginstallation which may, if required,

across whose secondary 9 is connected a heater 10 Wound around a ftemperature-sensitive resistor 11 with a substantial negativecoeflicient of resistance, suitably an element of the kind known as aBrirnistor, type CZ6, manufactured and sold by Standard Telephones andCables Limited. A shunt, including a manually variable resistor 12,permits of adjustment of the maximum heating of the resistor 11 andlimitation of its temperature rise.

A suitable resistor 11 of the aforesaid specific type has a resistanceof 3,000 ohms, i20%, kat 20 C. and 33 ohms, i20%, at 200 C. Suitably,the bias `heaterv10 has ak resistance of ohms when cold. It may, forexample, comprise approximately@ inches of nickel-chrome wire of0.006'inch diameter Wound in 40 turns, separated from cach other, in asingle layer over an insulating layer of f glass tape, 0.003 inch thick,wound around the resistor ,11.

' ment for a compartmental railway coach the main heat- Suitably, theresistor 11, wound with the insulating layer and bias rheater 10, is,Vmounted in an upright position on a smallfheat-resistant panel insideanopen-sided casing. The resistor 11 may be releasably held on the panelby a simple spring clip engaging over the upper end of the resistor. f Yf The resistor 11 itself serves as a diverter to divert a variableproportion of the bias current. supplied to the heaters'l of the mainthermostats. To modify the diverting action of the resistor 11 independence upon the temperature setting of the switch 2, the latter hasa second component 2a by which additional series resistance 13 can beintroduced into the diverter circuit through the element 11 as theresistance controlled by the switch y 2 itself is reduced. Trimmingresistors 14 permit of line rated by, for example 3.6 F. The controlcircuit including -the bias heaters 1 is supplied from a source ofreguadjustment of the settings of the thermostats and of compensationfor slight variations in bias sensitivitybetween one thermostat andanother. The normal use of these l t 3 resistors 14 makes Very littlediierence to the compensating action produced by the element 11.

The manner of operation is as follows:

As more heaters 5 areswitched on, the current through the heater 1t)increases proportionately, the resistor lll is heated and its resistancedecreases, diverting an increasing proportion of the bias current fromthe thermostat heaters 1 and raising the settings of the mainthermostats.

The resistors 13 reduce the diverting effect of the resistor 11 in themedium and low positions of the main switch 2, thus compensating for thefact that it requires less shunting resistance across the bias heaters 1to change the thermostat setdown by 5 F. from, say, 13 to 8 F. than from5 to 0 F.

If the setdown of the main thermostats obtained with the aboveedescribedarrangement, for the low, medium and high positions of the switch 2, isplotted against the amount of reheat expressed as a percentage of thetotal reheat available on the coach, it is found that the setdown variesapproximately proportionately with the amount of reheat, or at leastsuliciently so for practical purposes, the three curves obtained beingalso substantially parallel to one another.

If the supply to the heaters 5 is direct current, a diverter may beused, in place of the'transformer 8, 9, for supplying the heater 1). Theshunt resistance 12 is then replaced by series resistance.

We claim:

l. A vehicle having means dividing it into a plurality of compartmentsprovided with a common air-conditioning or air-heating equipment, meansfor supplying air from the said equipment to said compartments of thevehicle, electrical heating means for said individual compartments, asupply circuit for the said heating means, individual control means forthe said heating means in respective compartments, and automatictemperaturecontrol means comprising at least one main thermostatcontrolling operation of the said equipment, an electrical bias heateron the said thermostat, a supply circuit for the said bias heaterincluding a temperature-sensitive resistor with a negative coecient ofresistance, electrical heating means for the said resistor, and meanscoupled to the first-named supply circuit for supplying to the lastnamedheating means a current dependent upon the total heating currentsupplied to the first-named heating means, whereby the said resistor isitself heated to an extent dependent upon the said total current.

2. A vehicleas claimed in claim l, wherein the said last-named heatingmeans, in close proximity to which the said resistor is disposed, is aheater to which a current proportional to the said total current issupplied.

,3. A vehicle according to claim l, wherein the said temperature-controlmeans further comprises adjustable means for varying the setting of thesaid thermostat for maintaining diiferent temperature values of the airsupplied to the compartments by the said equipment and adjustable meansfor varying the heating eiect of the said 'resistor upon the saidthermostat in co-ordination with the adjustment of the said means forvarying the setl ting of the said thermostat.

4. A vehicle according to claim l, wherein the said resistor is arrangedas a diverter across the said bias heater on the said thermostat.

5. A vehicle as claimed in claim 1, wherein the said temperature-controlmeans further comprises adjustable means for varying the setting of thesaid thermostat by varying resistance in series with the said biasheater and means, adjustable in conjunction with the first-named means,for varying vthe'heating effect of the said resistor upon the saidthermostat by varying resistance in series with the said resistor.

6. A vehicle as claimed in claim 1, wherein an adjustable shunt isconnected across the said resistor.

References Cited in the le of this patent UNITED STATES PATENTS

1. A VEHICLE HAVING MEANS DIVIDING IT INTO A PLURALITY OF COMPARTMENTS PROVIDED WITH A COMMON AIR-CONDITIONING OR AIR-HEATING EQUIPMENT, MEANS FOR SUPPLYING AIR FROM THE SAID EQUIPMENT TO SAID COMPARTMENTS OF THE VEHICLE, ELECTRICAL HEATING MEANS FOR SAID INDIVIDUAL COMPARTMENTS, A SUPPLY CIRCUIT FOR THE SAID HEATING MEANS, INDIVIDUAL CONTROL MEANS FOR THE SAID HEATING MEANS IN RESPECTIVE COMPARTMENTS, AND AUTOMATIC TEMPERATURECONTROL MEANS COMPRISING AT LEAST ONE MAIN THERMOSTAT CONTROLLING OPERATION OF THE SAID EQUIPMENT, AN ELECTRICAL BIAS HEATER ON THE SAID THERMOSTAT, A SUPPLY CIRCUIT FOR THE SAID BIAS HEATER INCLUDING A TEMPERATURE-SENSITIVE RESISTOR WITH A NEGATIVE COEFFICIENT OF RESISTANCE, ELECTRICAL HEATING MEANS FOR THE SAID RESISTOR, AND MEANS COUPLED TO THE FIRST-NAMED SUPPLY CIRCUIT FOR SUPPLYING TO THE LASTNAMED HEATING MEANS A CURRENT DEPENDENT UPON THE TOTAL HEATING CURRENT SUPPLIED TO THE FIRST-NAMED HEATING MEANS, WHEREBY THE SAID RESISTOR IS ITSELF HEATED TO AN EXTENT DEPENDENT UPON THE SAID TOTAL CURRENT. 